OBJECTIVE This study aimed at evaluating the usefulness of determining cerebrospinal fluid (CSF) interleukin-6 (IL-6) concentration in adults with purulent, bacterial meningoencephalitis. METHODS A study group consisted of 16 patients hospitalized in the Department of Infectious Diseases of the Medical University of Silesia in Bytom in 2008 - 2012 due to purulent, bacterial meningoencephalitis. All of them were classified into two groups based on clinical severity, assessed on admission: group I - severe condition, group II - moderately severe or mild condition. CSF IL-6 concentration was measured in all patients on the first day of hospitalization. RESULTS Mean concentrations of IL-6 in CSF were assessed at 391.54 pg/mL and 110.51 pg/mL in patients in severe (group I) and moderately severe or mild condition (group II), respectively. Differences between CSF mean concentrations of this cytokine in both groups were statistically significant (p<0.01). No correlations between CSF IL-6 concentrations and other CSF inflammatory parameters were determined. Control testing performed in 5 patients of group I revealed only slight decrease of CSF IL-6 concentration in fatal cases. In case of patients who recovered from disease, IL-6 concentration in CSF was evidently decreased compared to its initial value. CONCLUSIONS Results suggest the usefulness of determining CSF interleukin-6 concentration to estimate inflammation intensity in the subarachnoid space, and indirectly, patient's clinical severity. IL-6 concentration may be also of prognostic importance in purulent, bacterial meningoencephalitis.